Isomerization of paraffin wax



Patented Feb. 9, 1954 UNITED STATES PATENT OFFICE ISOMERIZATION OF PARAFFIN WAX Delaware No Drawing. Application January 12, 1953, Serial No. 330,894

4 Claims.

This invention relates to a new and useful process for the isomertzation of paraffin wax. The invention also relates to a process for the production of lubricating oil and isoparafiin wax from paraflin wax. The invention also relates to novel lubricants.

This application is a continuation-in-part of our copending application, Serial Number 241,898, filed August 14, 1951.

Parafiin wax is a normally solid wax-like substance composed of high molecular weight hydrocarbons. It is called paraffin wax to distinguish it from the vegetable and animal waxes which are composed largely of oxygenated compounds. It is usually obtained from the heavier fractions of petroleum such as are used for the production of lubricating oils as well as certain burnin oils. In nearly every case, it is an undesired constituent in such oils and is removed by known so-called dewaxing methods during rcfining. While paraflin wax is useful for many purposes such as sealing containers, production of waxed paper, production of Water-proofed cartons and the like, and finds a large and wide use,

there is still a considerable amount of paraffin wax for which there is no ready market.

Various processes have been proposed for the treatment or conversion of paraiiin wax. Those processes resulting in a hydrocarbon product generally involve a refining operation which produces a normally solid wax of impproved characteristics, or a more drastic conversion treatment which results in the production of a liquid product. The former usually comprises such steps as solvent extraction, fractional crystallization, clay treatment and the like, in which the structure of the hydrocarbons is unaltered. The latter involves a step in which the hydrocarbons are decomposed or split to give a wide range of products comprising normally gaseous and normally liquid products, most of which are of relatively low value. It would be most advantageous to have a practical process whereby paraflin wax could be converted into more valuable hydrocarbon products. One possibility lies in isomerization.

By isomerization of paraffin wax is meant the treatment of the wax under conditions to isomerize the hydrocarbon constituents into isomers having the same molecular weight but a more branched structure. Some isomerization may take place in other drastic conversions of the wax but the term isomerization process is considered to designate only a process in which such isomerization to a more branched structure takes place to a substantial extent.

' able properties.

It is known that the melting points of the wax hydrocarbons are lowered upon isomerization to isomers having a more branched structure. Merely by way of example, normal hexacosane, a typical wax constituent, is a waxy solid having a melting point of 56 C. Whereas, its isomer 6,6 dipentyl hexadecane is a normally liquid compound having a melting point of C. Thus, by suitable isomerization a substantial conversion of even high molecular weight paraffin wax to a normally liquid product may be obtained. This liquid product is an oil having particularly desir- The isomerization can be accomplished and has been accomplished as described in U. S. Patent No. 2,475,358.

The main difiiculty encountered in attempts to isomerize parafiin wax is in preventing excessive degradation (cracking) to lower molecular weight products of little value. It is well known and generally recognized that the tendency for hydrocarbons to crack increases rapidly with increasing molecular weight. This holds both for thermal cracking as well as cracking induced by a cracking catalyst. Thus, whereas normal butane may be converted to isobutane quite selectively, the selective isomerization of parafiins of higher molecular Weight becomes increasingly difficult as the molecular weight is increased. In the method described in U. S. Patent No. 2,475,358, a fairly selective isomerization of paraftln wax is obtained by the use of Friedel Crafts-type catalyst which has been modified to decrease its cracking tendency and by simultaneous use of a large amount of a cracking-suppressor (decahydronaphthalene). While this method affords a moderate yield of lubricating oil of high viscosity index, and also diesel fuel of good cetane number, the recovery of the product requires special steps, and some catalyst is lost in each cycle. The process also involves the handling of corrosive liquids, and the isomerisation reaction is intrinsically slow so that large reactors are required.

Our above mentioned copending application describes a new process whereby paraffin wax may be isomerized quite selectively and at a much faster rate with the production of good yields of excellent oil and isoparaifin wax; the process is quite simple and no corrosive reagents are involved. In this process the paraflin wax is isomerized by treatment with a platinum-containing catalyst.

The process is applicable for the isomerization of any normally solid hydrocarbon wax. The wax willusually be derived from natural. mineral sources such as petroleum, oil shale, oil from tar sands, gilsonite, ozokerite, or the like, but synthetic wax produced by the Fischer-Tropsch synthesis or as a by-product of other processes may also be isomeriz'ed. The processmaybe applied for the isomer'ization of crude -so-called".sl'ack wax, or to refined waxes of various melting points or to so-called residue wax. While the various waxes difier somewhat in properties,.e..g.,.,melting point and hardness, they 'are'all "composed" of hydrocarbons containin-gilong paarafinic chains. In some paraflin waxes thezchain-s:maybslightly branched and in some .rthe i'chains ;may the attached to naphthenic orarornaticsgroupsi 01efinic groups are rarely present; when present they do not affect the operationrofthe process. ....In any case, the paraffin chain of the wax molecules can be isomerized to give a product having a more highly branched structure.

The parafiin wax is isomerized through the aid ss'ofea :supported platinum. reatalyst. *Ea-lladium or nickeltmaydoe substituted?forzpl atinumiiftdesired. ..'..'13he' zplatinurn may 5106 :applied iron 32. number of ,monventionalsoarrierramaterialsihithertn employed '1 :asa supportifor platinum catalyst. zsuitable sup- :1 ports; are :1 described .in "U. "S. matents cNumbers :2A783916 andi2;550,5.31.. Aluminaxis arpreferred .-:;support material. ":soecalled' activated ialumina Ftgamma; :alumina): .r-andxa'ctivated bauxite {3X6 zquite isuita'ble. tithe"aluminav should ibezsuhstan 2 iallyfreefofsalkaline:materialsasuchiiniparticular asithe:alkaliand;alkalineiearth:metals; Inmzfder -to insure ithezabsencerofi any'appreciabliezanroimts tofrsuch alkalinermaterialsiin the catalyst'zand to promote the catalystpitt-mayme desirable to treat 3% .the :carrier material iwith v.aszhalng'en :comp ound, a erg;v LT-IC1';I01 !I-IE,1ll3iOI'T toiincnrporatingithe ap'latiwmum. :i'EIEhezamount to i mlatinum irrxthe'rcatalyst ';:may vary; from iaifew shundredths :of 2a sperrcent,

rationzo'f iplatinumtis between about Tz1;% ;and

about 026%.

" .The platinum' may be applied toithe support in .-;:Arressential.featurenfithetprocess described in thescopending; applicationis "thatzthezisnmeriza- :5 ttion '1' is carried outxinj the presence inf. 5a :darge ..vamountofahydrogen.. E'Ihemolemat'm: of hydrogen do hydrocarbomshould "beat; least 7.1 and iprefereably above 5 .and mayabezmuch higher. lflmprac- .ticalmperation-matios vabove-300 are sometimes vrequired.

i In carrying out .the rprocess xtheswaxsis'ivaporwed in a suitable vaporizer, mixed-wwithctheihydrogen, and the mixture is passed .into'ccontact .with thecatalyst. The contact ismostrconven dandy-effected by supporting azbed of the catalyst in a reaction tubeandpassingtthe:vaporimixture vtzthrouglrthe bed. Theevapors'issuin'g from there Mention-tube are cooled to condense 'the'iproduct and"-the=gas is thenseparated from ithe conden- T658136; This gas is :recycled. :zDuring repeated recycling of the gas the hydrogen gradually becomes -.diluted with inert gases :produced 'nby the minor a-iiamount ofwsideireactionslin theprocess; This is 'not;particularlyzrjharmful as 'long-fa'siithe':speci ,,3;- temperaturesrand/or:flesser; .amountsiio gen. When the Wax isrsubstantially-reompletely fied minimum amount of hydrogen is applied. In order to prevent the dilution from becoming excessive, a small amount of the gas may be continuously withdrawn and replaced with fresh 5 hydrogen. .The'atemperatureein thef'bedis between L 300 C1and 550 C. and. is preferably between about 375 C. and about 490 C. The operation .:;:may be carried out under reduced pressure, at at- .unospheric pressure, or at considerably elevated.

*pressures; Pressures between about 50 and 3000 .s.irjgliarersuitable, pressures of the order of "300711110013. s.:i".rg. being generally preferred. Untm rder 'the conditions of temperature and pressure 5 "employed and in-the presence of the large amount of hydrogenj the wax is retained in the vapor 51v .phase.

@Under the described conditions, the isomerization takes place at a rapid rate. Thus a contact timeof the vapor mixture with the catalyst of 39 only a tenth of a second is sufficient in many scasesFtQzaflord a practical conversion. It-iis evi- 1ffifillfifiihiltWith-iJSlICh'flttes. asismall reactor, is *llallalbl'e'ffof ihandling a :large throughput-.1 :isong- 1 rermontact t-times'rmay, however; ibeiused particuiarly'rwhenr operating. at". .the :lower temperatures.

However, the contact time should-:rrotibmsoiiong at :any givensztemperaturexzto.tcause excessive "cracking; ,ZIhea:contact'tin'reimayfusuallyrbeiadjusted between 0.5 and 25,seconds intany case. to

leafiord the desirediconversion iwhile slimiting the 'iformation-tof'cracked'zproductsitorbelow 25% :and i preferablyrbelow about%% It ispointed..outiintsaidr copendmg application zthat :it isressentialtthat:processingvconditions applied ;:be ::.chosen .;.to insure; ;that cthe awax *ifeed :completely:incthetvapnriphase. E 111 iper'fecting he :process .itwaszfouudsthat'rif fihBWaXIWBQSlHOb zicomp'letely-"zzvaporized zinifthe :zreactionzrzone tthe iprocess-awastinoperaztive.

49 l Themrocessrof ouncopendingzapplication;isz'opaerating whenzthe wax isiicompletelyvvaporized as specificallyrecnmmended audit .isiapplicablerefor a :the isoinerizationmfmthe: wide range of:- waxes mentioned. :rewiu be appreciated', howeverythat ftlre process isemost: difliculmto'carry: out'when it is desirledto isomerize residueuwaxesrand *othersuch Waxes; havingimolec'ular wveightsiaboveezbout 500, rsincesuch waxes:aremexttoimpossible'tovaporize z, without'decomposition." .iThus'gforexamplegzin-Lthe $5 9 zisomerizationliof brightstock -wax a .ratio 10f hydrogenstowax'ofiover. 300'wasnecessary to insure :..the absence of 'a-"liquid lphaseiin' the: reaction .1' zone. lfccoinplete vaporizatiopn was not amainwtaineds thetrismall r amount of :liquid mistconstii' tutingithe least "volatile part ofrthe wax 'coll'ected sir on thex-catalyst. Alt soaked". into the cataiystrparxti'ol'es land was shortly A converted into 'tarry dexrposits 'wliich' blocked the :catalyst isurface. Also, :attempts to effect 'the isomerization by passing failed to give any appreciable amount oi isomerized product.""This-we now 'knowwas due'to the 1 fact "that" the short :contact times --f.ound "applimaple-mthe vapor phase "process were' entirely too short.

It "has now "been found that the' various parwaxes-can in fact-be effectively: and-advantageously' isomerized in the liquidfiphaset-lt is zfound that in order to -operatesuccessfiilly:inthe presenceof a liquid phase;'it=is' essential that the wax be 'retained substantially completely-" in a liquid phase, i; -e., -Ithe vaporization*of the'*wax 'must- .sbe repressed by the -'application: f lower ydro- Because of the large difierence between the volume of a given amount or in the liquid phase and in the vapor phase and because of the lesser amounts of hydrogen required, a reaction vessel of given size is capable of even greater production capacity when operating according to the present invention with the wax largely in the liquid phase.

The liquid phase operation in the present invention is not markedli superior to the vapor phase operation of the described copending application for the conversion of the lower molecular weight waxes such as the hard paraihn wax fobtained in the first dewaxing step in the dewaxing of petroleum lubricating oil, but it is vastly superior to the described vapor phase method for the treatment of the higher molecular weight waxes (e. g., having molecular weights above 500) and especially for the isomerization of residual waxes such as bright stock wax.

In the liquid phase isomerization process of the present invention any of the above mentioned waxes may be isomeriaed. same above-mentioned catalyst is employed. As pointed out, the isomerization rate when operating in the liquid phase is considerably lower than when operating in the vapor phase; thus. contact times of upwards of five minutes are required. The contact time in minutes for continuous liquid phase operation is calculated by dividing the volume of the catalyst used by the volume of liquid wax passed in contact with the catalyst per minute. In vapor phase operation the contact time is calculated by dividing the volume of the catalyst used by the volume of the vapor mixture contacted with the catalyst usedper minute. At these longer contact times there is a considerably greater opportunity for cracking reactions to take place. In view of this, and also to repress vaporization, it is desirable to retain the temperature somewhat lower than optimum for the vapor phase operation. The applicable temperature range is between about 300 C. and about 500 C. and the preferred temperatures are below about 490 C. The operation is preferably carried out under superatmcspheric.

pressure, e. g., above 100 p. s. i. g.

In the liquid phase method of the present invention the presence of hydrogen in the reaction zone is essential but the presence of a large amount of hydrogen is neither essential nor de sired Thus, mole ratios of hydrogen to wax between about 1 and 10 may be applied. Such low ratios can only be approached in the vapor phase process in the case of treating low molecular weight waxes that are easily vaporized.

In the liquid phase process the catalyst in the wax may be gradually passed through the bed from the bottom to the top concurrently with recycled hydrogen. In this method the catalyst bed is flooded with liquid wax. A preferred method is to allow the molten wax to trickle down through a fixed bed of pieces of the catalyst while hydrogen is passed through the bed either concurrently or countercurrently.

When treating a paraffin wax under the conditions above described, the product consists of normally liquid oil, unconverted wax, partially converted wax, and a small amount of cracked products. The small amount of cracked material may be distilled from the oil and wax. Depending upon the starting material and the degree of conversion, the total or distilled (as above) product may vary in consistency from a slurry or mush to a grease-like or plastic material. In some cases the product may be used as is without any further processing. In other cases, particularly where a crude wax feed was used, it may be desirable to refine the product by extraction, clay treating, chemical treatment or the like.

While the product may find application without further refinement, it will generally be desirable to separate it into two or more fractions. Thus, by employing conventional dewaxing techniques, a very high quality lubricating oil fraction may be separated. The pour point of the oil will depend in part upon the dewaxing conditions used and in turn the yield will depend in part upon the pour point chosen. Excellent yields of very low pour point oil of adequate viscosity for commercial usage and having a high viscosity index have been obtained from the product of a single pass isomerization treatment. In view of its very low pour point and very high viscosity index, the oil is particularly suited for many special purposes such, for example, as refrigerator lubricating oil and low temperature hydraulic fluids.

The wax remaining after separating the oil consists of unconverted and partially converted wax and the mixture has a lower melting point and softer consistency than the starting material. It may be used as such or retreated to produce additional amounts of oil.

While the wax may be used as such or recycled, it may also be separated by known techniques into a fraction of partially converted and a fraction of unconverted wax. Either of these fractions may be recycled. Isoparaiifin wax produced by the partial conversion of a wax consisting essentially of normal paraffins partakes somewhat of the characteristics of microcrystab line wax and may be used in place of microcrystalline wax. The isoparafiin wax differs from ordinary parafiin wax in having a much less brittle and more rubbery or plastic consistency. It resembles carnauba wax in its ability to absorb considerable quantities of oil without becoming sticky or tacky.

The amounts of the above products depend somewhat upon the character of the wax feed and largely upon the severity of the treating conditions (degree of conversion). When treating waxes under relatively mild conditions, only small amount of oil is formed; when treating under more severe conditions the amount of oil The liquid phase method of operation is particularly advantageous for the isomerization of high molecular weight waxes that are difiicult or impossible to vaporize. For example, the liquid phase method is particularly suited for the isomerization of so-called residue wax or bright stock wax. This waxyields novel and highly desirable lubricating oil; it is'most difiicult to treat irrthe vapor phase... Alsowhen treating this. high molecular weightmaterial, a small to. appreciable conversion tolower -molecular. .weight products by hydrocracking is not-detrimental asthe products remain: largely in the lubricating oil range; in fact, a highly desirable-and novel light lubricating oil is produced.

The. lubricating oils producedby the described process are novel oils having highly desirable properties When starting. with a .parafiinwax obtained from afirstdewaxing step and consisting almost completely of straight-chain parafiin hydrocarbons the lubricating oils. producedconsist largely of isoparafiin :hydrocarbons.-. While these isoparafiinshave a branched structure, they do nothave the complicated structure obtained byithexpolymerization of olefins, e. g., isobutylene and, consequently, they are. more. thermally stable. While the lubricating oil consists largee lypiisoparafiins it will. be noted thatit contains appreciable amounts .of aromatic constituents, thisis especially the case when the oil isproduced fromlresidue waxes; The oil obtainedby alumia numy-chloride. isoinerization is freeof aromatic constituents and is, therefore, quite difierent. Also; the product differs from the lubricating oil produced by the isomerization of parafin Wax using aluminum chloride with decahydronaphthalene (or cyclohexane) as a cracking suppressorias described inthe above-mentioned patent since the-product ofnthis patented process containsappreciable amounts of alkylationrcom densationproducts of the decahydronaphthalene.

When starting-with'a residuewax such as bright stock: wax: the lubricating. oils produced alsodifiernfrom: those produced by other;meth.- odsr' they; consist predominantly of hydrocarbons .1 having a cyclo-parafiin nucleus with attached long isoparafiin side- :chains. They alsoucontain appreciable amounts of-hydrocar" b01115 having. an aromatic nucleus. This latter type of 'hydrocarbonis not formed in the:aluminum chloride'process and if formed would be'lost in the aluminum chloride catalyst phase.

Example I .A hard, white, heavy/distillate. wax having the following properties wasyisomerized inthe' liquid phase:

Melting point ca; 70 (3. Molecular, weight ca. '500. nParafin .ca. 90%.

Run No 1, 904 2, 038. 2, 039

Temperature, ca. 400 450- 475 Pressure, p, s. i. g 500 500 500 H. S. V 2.5: 5.1 i 2 H2/Eeed,'M0le Rati ca. ca..15 02.. H2, Std. Ftfi/BbL. ea. 3, 200 ca. 3, 200 Products: 1 I

Gas-i-Loss, percent weight 4v 0 5. 0 7. 1 Below 300 0., percent Weight. 4. 3 10. 8 23. 1 Above 300 0., percent weight. 91.8 84; 2 69. 9 Analysis of-.300 O.+:

Aromatics, percent weight... 6. 4 12. 5 19. 7 Liquid saturates; percent 26. 3 24'. 9 37. 1

Weight. Wax, percent weight, 59. 0' 46.8 13.0 Aromatic Content of Oil above 10. 5 33. 4 34. 8

300 0., percent weight. Properties of Light Oil (300 Viscosity, 100 F., cs 4 61 4. 05 Viscosity, 210 F., 05.. 1 61 1. 46 Viscosity Index 2 106 Pour Point, F +40 +15 Properties of Heavy Lube Oil:

Viscosity; l00'F., es. ca. 19. 8. 24. 21. 33 V iscosity, 210 F., cs ca. 4. 37 4. 82 4.36 Viscosity Index... ca 138 136 131 Four Point, F.. ca 21 ---l Example II -Bright.stock .wax is .the veryhigh molecularweight wax obtainedfrom the residue remainingafterdistilling off the distillablelubricating.. oi1.fractionsfrom. a lubricating oilpetrolleumstock. The non-dstill'able. oil. (bright stock) in. this residueis particularly desired for certain purposes and .is in demand. A bright stock wax having theiollowing inspectiondatawas isomerized in. the liquid phase.

Density; g./ml. at 20": C 08899 Viscosity at 210 F. at A. S. T. M. D-445- 20 .50 Molecular weight; .cai T117 The conditions and results are shown in the following table:

Temperature, 0. Max Pressure; p. s. i. g Ha/Feed Mole Ra Space Velocity (L. H. S. V.) Light Lubricating Oil:

PercenttBy Weight of Charge. 20. 7 11.5 8. 7i 3. 0 VlSCOSltY, Gentistokes at 100. F 14 13 29 n 23 Viscosity Index" 122 116' 113 P0111. Point, "F +20. +25 T +20 Heavy Lubricating Oil:

Percent By Weight of Charge Viscosity, 0entistokes'at100F 244 338 366- '4b4 Viscositylndex .102. 93 93 PourPoint: +15 +25 +23 +25 time ofatleast 5 minutes but insufiicient. to produce more than 25% conversionto cracked prod.- ucts of lower molecular weight, cooling. the product, separating and recycling the hydrogen-containinggas, distilling the productv toremovera lubricating oil. distillate, and subjecting the. said distillate to a dewaxng. treatment toseparate unconverted wax' from the liquid oil.

2. Process for the conversion of brightstock waxzinto bright stock which comprises melting brightstock wax and contacting the liquid wax in the presence of at: least one mole of hydrogen per mole of. 'wax' with a supported. platinum catalyst'at a temperature between-raboutBOO? C. and about 500"C. and under a pressure betweenzabout 50 and 3000 p. s. i. g; forra contact time: of at least 5 minutes but insufficient to produce more than 25 conversion to cracked-products of lower molecular Weight, cooling the. product; separating and recycling the 'hydrogen containing gas; disfilling the productto remove distillable oil and dewaxing the residue to obtain'bright stock...

3. The process according to claim 1 further characterized in that the molten-'wax-is :passed in the liquid phase through a bedrof the catalyst under conditions'of time and temperature such that not more than 25% 'of'the'wax is :cracked to hydrocarbons lighter'than.lubricating.oil:

4. A lubricatingoilprepared by the process of claim 1.

GEORGE M. GOOD. JOHN W. GIBSON. BERNARD S. GREENSFELDER'.

Ref'erencesCited. in. the .file. of .thispatent UNITED." STATES PATENTS Number Name Date 2,461,453 Toettcher'et al; Feb. 8, 1949 2',475,358 4 Moore July'5, 1949 2,478,916 Haensel Aug 16,-'1949 

1. A PROCESS FOR THEPRODUCTION OF A LUBRICATING OIL FORM PARAFFIN WAX WHICH COMPRISES CONTACTING A MOLTEN NORMALLY SOLID PARAFFIN WAX IN THE LIQUID PHASE AND WITH AT LEAST ONE MOLE OF HYDROGEN PER MOLE OF WAX WITH A SUPPORTED PLATINUM CATALYST AT A TEMPERATURE BETWEEN ABOUT 300* C. AND ABOUT 500* C. AND UNDER A PRESSURE BETWEEN ABOUT 50 AND 3000 P.S.I.G. FOR A CONTACT TIME OF AT LEAST 5 MINUTES BUT SUFFICIENT TO PRODUCE MORE THAN 25% CONVERSION TO CRACKED PRODUCTS OF LOWER MOLECULAR WEIGHT, COOLING THE PRODUCTS, SEPARATING AND RECYCLING THE HYDROGEN-CONTAINING GAS. DISTILLING THE PRODUCT TO REMOVE A LUBRICATING OIL DISTILLATE,, ADN SUBJECTING THE SAID DISTILLATE TO A DEWAXNG TREATMENT TO SEPARATE UNCONVERTED WAX FROM THE LIQUID OIL. 